Fan with stepped diameter expansion

Abstract

The invention relates to a fan, in particular an axial or mixed-flow fan, with a housing and an impeller arranged in the housing and driven by an electric motor, with blades extending between a hub ring and a cover ring, in which a stepped diameter expansion in the form of an abrupt expansion of the flow cross section in the flow direction is formed downstream in the flow direction of the impeller and after the outlet area of ​​the cover ring.

Description

[Technical field]

[0001] The present invention relates to a fan, in particular an axial or mixed flow fan. The fan has a housing and an impeller disposed within the housing and rotatably driven by an electric motor. The impeller also has blades extending between the hub ring and the cover ring. [Background technology]

[0002] Fans of this general type are known in commercial use and come in a wide variety of designs. For example, there are fans that have an axle wheel that does not have a covering and that operate within a housing. In this case, the noise level can increase dramatically due to pressure build-up or pressure loss within the housing. As the pressure increases, the noise level increases significantly.

[0003] For fans with freely rotating mixed flow wheels, a problem arises when there is little space available laterally. Furthermore, such fans have problems in terms of power and noise levels when the pressure is too low.

[0004] For general prior art information, see US Pat. No. 5,399,633. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 015792(A1) Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to overcome or at least mitigate the shortcomings or problems of the prior art. In particular, the aim is to provide a particularly quiet and efficient fan which does not react sensitively to pressure increases, in terms of noise generation and pressure increase. Additionally, the fan of the present invention is intended to be different from competing products. [Means for solving the problem]

[0007] The above mentioned object is achieved by the features of claim 1. In the case of a fan according to the feature of claim 1, a "step-shaped diameter expansion portion" in which the flow cross section is suddenly expanded is formed downstream of the impeller and downstream of the outlet region of the cover ring in the flow direction. According to the present invention, the drawbacks of the prior art are substantially eliminated by providing a stepped diameter expansion portion in the shape of an abrupt expansion of the flow cross section. This solution is simple and effective when pressure increases.

[0008] Experiments have shown that it is effective when the cross-sectional step associated with the stepped diameter expansion portion has an area ratio of 105% or more, and particularly 110% or more. This results in an enlarged cross section in the flow passage downstream of the impeller.

[0009] The fan according to the invention has a cylindrical housing, and a stepped diameter expansion can be implemented downstream of the outlet of the cover ring.

[0010] In particular, the contour of the covering interacts with the contour of the housing for both the primary and secondary flows within the fan, and the imaginary downstream extension of the contour of the covering does not intersect with the inner contour of the housing.

[0011] Furthermore, in the fan of the present invention, the main flow enters the impeller through an inlet nozzle. The main flow flows through the housing via an inner through-flow region and an outer through-flow region. A secondary flow, as a partial flow of the air leaving the impeller, flows back between the cover ring and the contour of the housing and enters again into the region of the impeller via the radial gap between the inlet nozzle and the cover ring. This secondary flow is a small partial flow compared to the air flowing out of the impeller, and can influence the main flow in the region close to the surrounding covering and stabilize the flow there. In addition, the secondary flow is periodically given strong vortices due to the effect of the rotational motion of the impeller.

[0012] A redirecting support device, which may have additional support features, may be located downstream of the impeller in the flow direction. This redirecting support device then influences the flow in the area of ​​the stepped diameter expansion. Additionally, the redirection support device and the stepped diameter expansion interact to affect the secondary flow, which causes the main flow to "suck" into the inner contour of the housing. Furthermore, swirl is imparted to the flow exiting the impeller. Additionally, the design of the intermediate ring of the redirection support device may affect the flow in the area of ​​the stepped diameter expansion, with the intermediate ring being oriented at a pitch angle to the flow direction rather than parallel to the axial direction. In this way, pressure recovery results in a quieter and more efficient fan.

[0013] Furthermore, the redirection support device may be provided as an integral part of the housing, which is preferably manufactured by plastic injection molding. Furthermore, by manufacturing the housing in this manner, a lightweight design is possible, and the housing can be manufactured in an advantageous manner.

[0014] Furthermore, the support function for the motor and the impeller may be performed by a special suspension made of steel or other metallic material. The mechanical properties, especially the stability, play a particular role here.

[0015] For cooling purposes, the hub ring of the impeller may have a large central opening towards the rotor of the electric motor, so that motor cooling is particularly facilitated.

[0016] Furthermore, the ratio of the outlet diameter at the outlet end of the housing to the inner outlet diameter of the cover ring must not fall below a certain minimum value; in other words, this ratio must be greater than 1.05. This characterizes the flow passage downstream of the impeller as having an expanded cross section. Combined with the cylindrical inner contour of the housing, a stepped diameter expansion is created for the main flow downstream of the impeller.

[0017] The impeller covering may extend beyond a region substantially parallel to the impeller axis or at a small pitch angle relative to the impeller axis. Furthermore, the impeller hub ring may have the distinct feature of increasing diameter in the flow direction. This configuration also promotes flow.

[0018] Additionally, the exit diameter of the inlet nozzle is slightly smaller than the exit diameter at the impeller covering. This configuration is preferred when the ratio of the outlet diameter of the housing to the outlet diameter of the inlet nozzle is greater than 1.05.

[0019] Further, a plurality of openings may be formed in the housing, the openings fluidly connecting the area associated with the secondary flow between the inlet nozzle or impeller covering and the housing to an area outside the housing.

[0020] Thus, there are various ways to embody and develop the present invention. For this purpose, reference is made to the claims dependent on claim 1 and the following description of embodiments of the fan according to the invention with reference to the drawings, in which: General improvements and developments are also described in connection with the description of embodiments of the invention with reference to the drawings. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a perspective view of a fan according to the present invention, seen from the outflow side and in section along a plane through the fan axis, the fan having an impeller with a covering ring circumferentially enclosed within a housing, and a redirection support device. [Diagram 2] FIG. 2 is a perspective view of the fan in FIG. 1 as viewed from the inlet side. [Diagram 3] FIG. 3 is a perspective view of the fan of FIGS. 1 and 2 as viewed from the outflow side. [Figure 4] FIG. 4 is a side view of the fan and housing of FIGS. 1, 2 and 3 in section through a plane through the fan axis, with important diameters indicated; [Diagram 5] FIG. 2 is a perspective view of a further embodiment of a fan according to the invention, seen from the outflow side, in section along a plane through the fan axis, in which an opening is provided in the housing; [Figure 6] FIG. 2 shows a perspective view of a further embodiment of a fan according to the invention, sectioned according to a plane through the fan axis, seen from the outlet side, in which the housing is provided with vortex correction elements; [Figure 7] FIG. 2 shows a perspective view of a further embodiment of a fan according to the invention, seen from the outlet side in section according to a plane through the fan axis, with vortex correction elements on the housing extending axially beyond the impeller; [Figure 8] FIG. 5 is a plan view of the fan of FIGS. 1 to 4, viewed from the outflow side. [Figure 9] 4 shows a plan view from the outlet side of another fan according to the invention, with alternating inclinations of the support elements; FIG. [Figure 10]FIG. 2 shows a perspective view of a further embodiment of a fan according to the invention, sectioned according to a plane through the fan axis, seen from the outflow side, in which no guiding device is provided, the support function being taken over by the suspension; [Figure 11] FIG. 2 shows a perspective view of a further embodiment of a fan according to the invention, sectioned according to a plane through the fan axis, seen from the outflow side, where an inward direction device is provided and where a suspension assumes the support function; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] FIG. 1 shows a perspective view of a fan 1 according to the invention having a housing 2, seen from the outflow side and in section along a plane through the fan axis. The redirecting support device, i.e. the guide device 15, is manufactured integrally with the housing 2 by plastic injection molding and is essentially composed of a hub ring 4, an intermediate ring 5, guide vanes 3 extending therebetween, and support vanes 3a extending between the intermediate ring 5 and the inner contour 11 of the housing 2.

[0023] The impeller 19 is comprised of a hub ring 21, a circumscribing cover ring 16, and blades 22 extending therebetween. The blades 22 are in turn fixed to the hub ring 21 by fixing devices 30 (FIG. 2) on a rotor 35 of a motor 34 (here advantageously an external rotor motor). In operation, the impeller 19, driven by the motor 34, rotates about the fan axis to transport air or other transport medium from an inlet side to an outlet side (generally from left to right in FIG. 1).

[0024] On the inlet side there is an inlet nozzle 9, the outlet end 37 of which is located radially inside the cover ring 16 of the impeller 19, with a radial gap being formed between the inlet nozzle 9 and the cover ring 16. The inlet nozzle 9 is fixed to the housing 2 and is formed as an integral component therewith. The guide device 15 together with an air duct (outer through-flow area) 6 is arranged in the housing 2 downstream of the impeller 19 , such that an air flow is formed between the intermediate ring 5 of this guide device 15 and the inner contour 11 of the housing 2 . A portion of the air flowing from the impeller 19 flows through the air duct 6 . The other portion of the air flowing from the impeller 19 flows through the inner through-flow region 7 . This inner through-flow region 7 is bounded by the hub ring 4 of the guide device 15 when viewed in the span width direction towards the fan axis, and by the intermediate ring 5 when viewed in the span width direction towards the outer through-flow region 6. The inner through-flow region 7 is interspersed with guide vanes or guide elements 3 (in the embodiment 17, advantageously 9 to 23). The flow, which flows near the axis and is imparted with swirl, exits the impeller 19 and enters the guiding device 15, and is stabilized by the guide vanes, i.e., the guide elements 3, by reducing swirl in the flow and backflow in the hub area. This increases efficiency.

[0025] The hub ring 4 and the intermediate ring 5 of the guiding device 15 extend almost completely around the axis. The hub ring 4 surrounds an inner receiving area 8 in which, for example, a drive motor 34 of the fan 1 having a stator 36 can be arranged. Either no flow passes through the inner receiving area 8 or a small amount of air flow (0.1% to 2% of the total air flow) passes through the inner receiving area 8 to allow for removal of waste heat generated by the motor 34. And flow through the inner receiving area 8 can also occur in the direction opposite to the main transport direction if the flow is caused by a pressure difference between the outflow and inflow sides.

[0026] In the outer through-flow region 6 there are fewer (from three to eight) support elements 3 a which provide a static connection between the intermediate ring 5 and the housing 2 . Due to the small number of support elements 3a, almost no additional noise is generated in this outer through-flow region 6 even if the flow exiting the impeller 19 interacts with the support elements 3a. In another embodiment, not shown, the support element, the support vane 3 a, may be arranged at a maximum distance from the impeller 19, i.e. almost close to the outlet end of the housing 2 or relatively close to the outlet end of the intermediate ring 5 of the guiding device 15.

[0027] Furthermore, the housing 2 including the support vanes 3a, the guide device 15 with the intermediate ring 5, the guide vanes 3 and the hub ring 4 can be manufactured in one piece by plastic injection molding. In that case, the inlet nozzle 9 is a separate part and is attached to the housing 2 after the impeller 19 has been inserted. Conversely, the inlet nozzle 9 can also be integrated into the housing 2 . In that case, the redirecting device 15 with the supporting vanes 3 a is a separate part which is fixed to the housing 2 when the impeller 19 is placed in the housing 2 .

[0028] During operation of the fan 1, a main flow passes through the inlet nozzle 9 and into the impeller 19 generally from left to right in FIG. 1 , then separates into an outer through-flow region 6 and an inner through-flow region 7, and exits the housing 2, and thus the fan 1, again at the outlet end 25 of the housing 2. At the same time, secondary flows exist. This secondary flow is a proportionally smaller partial flow of air which leaves the outlet end 32 of the impeller 19, flows back between the surrounding cover ring 16 of the impeller 19 and the inner contour 11 of the housing 2, and then re-enters the impeller 19 through the radial gap between the inlet nozzle 9 and the cover ring 16. This secondary flow stabilizes the main flow in the area close to covering 16 and has a significant influence on the main flow. This secondary flow is significantly influenced by the rotational motion of the impeller 19, and periodically vortices are imparted to it.

[0029] After leaving the outlet end 32 of the impeller 19, the main flow passes through a region where the flow cross section expands suddenly. In other words, a stepped diameter expansion portion is formed downstream of the impeller 19 . The increased cross section reduces the flow velocity, generates additional static pressure, increases the degree of recoil, and improves static efficiency. The low flow velocity also reduces noise generation in downstream components through which the flow passes, such as the redirection support device 15 with the guiding element 3 (optionally the support element 3a and the intermediate ring 5) or in the suspension.

[0030] It is a common assumption and practical prejudice among experts that such stepped diameter expansions are very inefficient at converting kinetic energy into pressure energy. However, there are several factors that make the stepped diameter expansion work well. Firstly, secondary flow effects cause a “suction” of the main flow towards the inner contour 11 of the housing 2 . Secondly, there is an effect that a strong vortex is imparted to the flow exiting from the impeller 19 . Thirdly, the design of the intermediate ring 5 of the redirection support device 15 makes it possible to specifically influence the flow in the area of ​​the stepped diameter expansion. In particular, it is advantageous if the intermediate ring 5 is not parallel to the axial direction but has a pitch angle relative to the axial direction.

[0031] Overall, the pressure recovery provided by the stepped expansion and the associated reduction in flow velocity results in a quieter and more efficient fan. In an embodiment, backflow in the hub region is further significantly reduced by the redirection support device 15 . Furthermore, the small number of support blades 3a ensures low noise.

[0032] By providing a stepped radial expansion instead of a conventional radial expansion, the inner contour 11 of the housing 2 can be made substantially cylindrical and not necessarily conical, as is the usual shape of a radial expansion. This greatly simplifies the manufacturability of the housing 2, both in plastic injection molding and also in sheet metal design.

[0033] FIG. 2 is a perspective view of the fan 1 having the housing 2 according to the invention of FIG. 1, seen from the inlet side. As a supplement to FIG. 1, it can be seen that the hub ring 21 of the impeller 19 is open over a large surface area in the central region to ensure that the air entering the rotor 35 of the motor 34 provides cooling. Thus, substantially the entire front surface of the rotor 35 is not covered by the inflow. The blades 22 of the impeller 19 are sickle-shaped at the rear, opposite the clockwise direction of rotation. This means that the radially outer blade region rotationally follows the radially inner blade region. However, the impeller 19 may also be sickle shaped at the front depending on the required operating environment. The housing 2 is provided with an inlet side fixing device 24 for fixing the fan 1 to an air treatment system or device, for example by means of screws. Likewise, the housing 2 is provided with an outlet fixing device 23 for fixing the fan 1 to an air treatment system or device, again for example by means of screws.

[0034] FIG. 3 shows a perspective view of the fan 1 having the housing 2 according to the invention of FIGS. 1 and 2, seen from the outflow side. 1 and 2, it can be readily seen that the stator 36 of the motor 34 is disposed within the inner receiving area 8 in the hub ring 4 of the redirection support device 15. As shown in FIG. The redirection and support device 15 has a number of inner guide vanes 3, for example 13 to 23, which suppress or at least reduce backflow that may occur near the hub. Further, in the outer through-flow region 6, a small number of support vanes 3a, for example, four to nine, are arranged. Here too, the presence of a stepped diameter expansion can be seen based on the distance between the outlet end 32 of the cover ring 16 of the impeller 19 and the inner contour 11 of the housing 2 .

[0035] FIG. 4 is a side view of the fan 1 and housing 2 of FIGS. 1, 2 and 3, in section taken along a plane through the fan axis 26. In addition to Figs. 1 to 3 the three diameters DA12, DL13 and DD14 as well as the outflow direction 31 of the covering ring are shown diagrammatically. These dimensions make it easy to characterize the stepped diameter expansion formed by the housing 2 and the cover ring 16 of the impeller 19 . DA12 is the outlet diameter of the housing 2, ie, the diameter at the outlet end 25 of the housing 2. DL13 is the inside diameter of the peripheral ring 16 at its outflow end 32. DD14 is the inside diameter of the inlet nozzle 9 at the outlet end 37. Advantageously, the ratio DA / DL is greater than 1.05, thereby characterizing a cross-sectional expansion in the flow passage downstream of the impeller 19 . Together with the substantially cylindrical inner contour 11 of the housing 2 a stepped diameter expansion is created for the main flow downstream of the impeller 19 .

[0036] The impeller 19 has a cover ring 16 which extends over a wide area approximately parallel to the fan axis 26 or which is arranged at a slight angle to the fan axis 26 . The hub ring 21 of the impeller 19 has a pronounced conical shape with a diameter increasing in the flow direction. The inner contour of the outlet end 32 of the cover ring 16 has a pitch angle relative to the fan axis. Thus, the geometric outflow direction 31 from the impeller 19 is not parallel to the axial direction, but is slightly radially outward relative to the flow direction when viewed in plan cross section, at an angle of approximately 5° to 15°. Such an angle is advantageous for the operation of the special stepped diameter expansion section. Furthermore, an imaginary extension 31 of a tangent to the inner contour of the cover ring 16 (the geometric outflow direction at the outflow side end 32 of the cover ring 16 ) does not intersect with the inner contour 11 of the housing 2 . As a result, the flow in the vicinity of the cover ring is given a curvature towards the inner contour 11 of the housing 2, which favours efficient operation of the stepped diameter expansion.

[0037] The outlet diameter DD14 of the inlet nozzle 9 is slightly smaller than the outlet diameter DL13 on the cover ring 16 of the impeller 19. In the case of a more mixed flow impeller 19 having a cover ring 16 with a more conical shape, DD14 may be significantly smaller than DL13. In both cases, DD14 is generally significantly smaller than the exit diameter DA12, and in particular it is advantageous if DA / DD>1.05. This allows the contour of the inlet nozzle 9 to be contained in the radial region between the diameters DD14 and DA12. As a result, the inner contour 11 of the housing 2 is generally cylindrical, with the inlet nozzle 9 having a radially interior space therein.

[0038] FIG. 5 shows a further embodiment of a fan 1 according to the invention in a perspective view from the outflow side, sectioned along a plane through the fan axis, in which the housing 2 is provided with a number of openings 17 . Furthermore, this embodiment is equivalent to the embodiment of FIGS. The openings 17 connect the areas for secondary flows between the inlet nozzle 9 and the housing 2 or between the covering 16 of the impeller 19 and the housing 2 with areas outside the housing 2 . Depending on the mounting manner of the fan, the pressure level in the area outside the housing 2 in the area of ​​the opening 17 can match the pressure level on the inlet or outlet side of the fan or can have an independent pressure level if it is separated from the fan 1 or from its inlet and outlet sides.

[0039] In the area of ​​the outer opening 17 of the housing 2, flow conditions are typically such that there is little swirl about the fan shaft or the flow velocities are generally low. As shown in FIG. 1, the recirculation flow (secondary flow) generated from the outlet of the impeller 19 may have strong vortexes. In this regard, the mixing of the swirl-imparted recirculation flow with the lower vorticity vortex flow entering the recirculation zone through openings 17 compensates for or reduces the vortex flow entering the impeller 19 as a secondary flow through the radial gap between the inlet nozzle 9 of the impeller 19 and the cover ring 16. This can be advantageous in avoiding spalling at the covering 16 or vanes 22, and therefore contribute to achieving high efficiency with low noise.

[0040] FIG. 6 shows a further embodiment of a fan 1 according to the invention in a perspective view from the outlet side in section through the fan axis, in which the housing 2 is provided with a vortex correction element 20 . The vortex correction element 20 is formed axially in the region of the inlet nozzle 9 and / or the covering ring 16 of the impeller 19 . Viewed axially, the vortex correction element 20 overlaps the radial gap between the inlet nozzle 9 and the cover ring 16 . The eddy current correction element 20 projects radially inwards from the inner contour 11 of the housing 2 . Alternatively, a similar element can be attached to the inlet nozzle 9 on the side facing the housing 2 . The shape of the vortex correction element 20 may be straight and parallel to the fan axis, as shown in the figure. Curved or otherwise optimized shapes may also be advantageous. The function of the swirl compensation element 20 is to reduce strong swirls which are secondary flows entering the impeller 19 through the radial gap between the inlet nozzle 9 and the covering 16 of the impeller 19 . This can be advantageous in avoiding spalling at the covering 16 or vanes 22, and therefore contribute to achieving high efficiency with low noise.

[0041] FIG. 7 shows a further embodiment of a fan 1 according to the invention in a perspective view from the outlet side in section according to a plane through the fan axis, in which a relatively long vortex correction element 20a on the housing 2 extends axially beyond the impeller 19 or its covering 16. A relatively long swirl correction element 20 a can reduce swirl more significantly and positively affect the main flow exiting the housing 2 at the outlet end 25 after exiting the impeller 19 . In order to avoid too high vortex components, especially in the region of the inner contour 11 of the housing 2, the main flow can be directed parallel to the axial direction.

[0042] FIG. 8 is a plan view of the fan 1 of FIGS. 1 to 4 as viewed from the outflow side. As a complement to Figures 1 to 4, it can be easily seen that the support vane 3a, as far as its radial shape is concerned, is relatively strongly twisted / inclined compared to an imaginary radial line from the fan axis. In the planar projection rear view of FIG. 8, the angle between the inlet end of the support blade 3a and an imaginary radial line from the fan shaft is generally or on average greater than 25°. The support vanes 3a are highly inclined or sickle-shaped. This reduces the generation of rotation noise. In an embodiment, the support vanes 3 a are inclined counterclockwise in a radially inward to outward direction, which is opposite to the direction of rotation of the impeller 19 . However, the support blades 3a may be inclined in other directions. All the support vanes 3a are inclined in the same direction. In contrast to this configuration, the inner guide element 3 is slightly inclined in the radial direction. In the radially inner region, the velocities occurring in the circumferential direction (local rotational speed or flow velocity of the blades 22 of the impeller 19) are lower, so that the generation of rotational noise is less important here. On the other hand, an arrangement of the inner guiding element 3 at a closer radial angle is advantageous for static stiffness, since the inner guiding element 3 also has a supporting function.

[0043] FIG. 9 shows a plan view from the outflow side of a further embodiment of a fan 1 according to the invention, in which the support elements 3a are alternately inclined in the circumferential direction. Each support element 3a is highly inclined relative to the radial direction when viewed at its leading or trailing edge. However, the tilt direction, i.e. the sign of the tilt angle, differs from one support element 3a to another. This can be beneficial for the stiffness of the system. 3, since the supporting vanes 3 a are here designed to have a supporting function, ie towards the outside of the housing 2 they are responsible for the static connection of the motor 34 with the impeller 19 . The inclination directions of the support blades 3a are alternately changed, so that they reinforce each other in the same way as in the case of a lattice structure. Other than the above, the design is consistent with FIGS. 1 to 4 and 8.

[0044] FIG. 10 shows a further embodiment of a fan 1 according to the invention in a perspective view from the outflow side, in section according to a plane through the fan axis, in which no guiding device 15 is provided. The suspension 27 provides a support function. The suspension 27 is advantageously made of steel or other metallic material, so as to achieve the necessary stiffness with a small cross-sectional area, thereby minimizing noise generation. Such suspensions 27 may be inclined relative to the radial direction and / or may have a cross-sectional shape that is aerodynamically optimized. It is also conceivable for the suspension 27 to incorporate a contact protection grid. The suspension 27 is fixed to the housing 2 by means of a fixing device 28 and screwed in place. Downstream of the outlet end 32 of the cover ring 16 around the impeller 19, the flow cross-sectional area expands rather abruptly to the larger cross-sectional area of ​​the inner contour 11 of the housing 2, forming a sort of stepped diameter expansion for the main flow.

[0045] FIG. 11 shows a further embodiment of a fan 1 according to the invention in a perspective view taken from the outflow side in section along a plane through the fan axis, in which an inner guiding device 15 is provided and in which a suspension 27 assumes the support function. Therefore, the support blade 3a is not formed. This embodiment is similar to the embodiment shown in FIG. 10, except that the inner redirecting wheel 15 formed together with the intermediate ring 5 and the guide element 3 prevents or reduces backflow in the hub area, thereby improving efficiency.

[0046] For further advantageous refinements of the fan according to the invention, reference is made to the general part of the specification and to the appended claims, in order to avoid repetition.

[0047] Finally, the above-described embodiments of the fan according to the present invention are intended to be teaching and not limiting of the present invention. [Explanation of symbols]

[0048] 1. Fan 2. Housing 3 Guide element (inner guide vane) 3a Support element (support blade) 4. Hub ring for guide device 5. Intermediate ring of guide device 6. Outer through-flow area (air duct) 7...Inner flow area 8. Medial receptive area of ​​the hub ring 9. Inlet nozzle 10. Hub ring for guide device 11...Inner contour of housing 12...Outside diameter of housing 13...Outer diameter of impeller 14...Outer diameter of inlet nozzle 15 Redirection support device (guiding device) 16 Cover ring surrounding the impeller 17 Housing opening 18....Inner suspension fixing device 19 Impeller 20...eddy current correction element 20a Long eddy current compensation element 21 Impeller hub ring 22 Impeller blades 23 Outlet side housing fixing device 24 Inlet side housing fixing device 25 Outlet end of housing 26 Fan shaft 27 Suspension 28....External suspension fixing device 30 Motor fixing device on impeller 31 Covering flow direction 32 Outlet end of covering 34 Motor 35 Motor rotor 36 Motor stator 37 Outlet end of inlet nozzle

Claims

1. A fan having a housing and an impeller disposed within the housing and rotatably driven by an electric motor, the blades extending between a hub ring and a cover ring, A fan, wherein a stepped diameter expansion portion in the shape of a flow cross section that suddenly expands is formed downstream of the impeller and downstream of the outlet region of the cover ring in the flow direction.

2. 2. The fan according to claim 1, wherein the cross-sectional step of the stepped diameter expansion portion is characterized by an area ratio of 110% or more.

3. 3. A fan according to claim 1 or claim 2, characterized in that the inner contour of the housing is substantially cylindrical.

4. the contour of the cover ring interacts with the inner contour of the housing with respect to the primary and secondary flows; 2. The fan according to claim 1, wherein an imaginary downstream extension of the contour of said cover ring does not intersect with the inner contour of said housing.

5. the main flow enters the impeller through an inlet nozzle and flows through the housing via an inner through-flow region and an outer through-flow region; 5. A fan according to claim 4, characterized in that the secondary flow, as a partial flow of air leaving the impeller, flows back between the cover ring and the inner contour of the housing and re-enters the region of the impeller through the radial gap between the inlet nozzle and the cover ring.

6. 2. A fan according to claim 1, characterized in that a redirecting support device for influencing the flow in the region of the stepped diameter expansion is arranged downstream of the impeller in the flow direction.

7. the redirection support device is integrated into the housing; 2. The fan according to claim 1, wherein the housing is manufactured by plastic injection molding.

8. 2. A fan according to claim 1, characterized in that the support function for the electric motor and the impeller is performed by a suspension made of steel or other metallic material.

9. 2. A fan as claimed in claim 1, characterized in that the impeller hub ring has a large central opening towards the rotor of the electric motor for cooling purposes.

10. 2. A fan as claimed in claim 1, wherein the ratio of the outlet diameter at the outlet end of the housing to the outlet diameter inside the impeller cover is greater than 1.

05.

11. the impeller covering extends beyond a region substantially parallel to the impeller axis or at a small pitch angle relative to the impeller axis; 2. A fan as claimed in claim 1, characterized in that the impeller hub ring has a pronounced conical shape with a diameter increasing in the direction of flow.

12. 11. The fan of claim 10, wherein the coverings facing radially outward near the outlet end have a greater pitch angle relative to the fan axis of between 5° and 15°.

13. 6. A fan as claimed in claim 5, wherein the outlet diameter of the inlet nozzle is at least slightly smaller than the outlet diameter of the impeller covering, and the ratio of the outlet diameter of the housing to the outlet diameter of the inlet nozzle is greater than 1.

05.

14. 5. The fan of claim 4, wherein a plurality of openings formed in the housing fluidly connect the area associated with the secondary flow between the inlet nozzle or impeller covering and the housing to an area outside the housing.

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